There is known an electrocardiographic signal detection device for extracting the activity of a human heart as an electrocardiographic signal, and acquiring biological information, such as electrocardiographic data, based on the electrocardiographic signal for the purpose of diagnosis, treatment, etc. of heart diseases.
That type of electrocardiographic signal detection device is classified into a large-scaled device that is used by doctors in medial institutions, e.g., hospitals, and a portable device that is used by ordinary persons in homes.
The large-scaled electrocardiographic signal detection device includes, for example, a desktop computer having a sophisticated processing function to analyze the electrocardiographic data, a plurality of, e.g., twelve, electrodes connected to the computer through respective cables, a desktop display device for monitoring electrocardiographic waveforms, etc., and a printer for printing out the electrocardiographic waveforms, etc. A doctor, for example, attaches the electrodes to the legs and arms of a subject (examinee) lying on a bed, and operates the computer. Responsively, the electrocardiographic signal detection device detects the electrocardiographic signal of the subject and precisely performs an analysis of the electrocardiographic data, etc., thereby generating professional information that is directly useful for, e.g., diagnosis and treatment of arrhythmia (irregular pulse), angina pectoris (stricture of the heart), etc.
On the other hand, the portable electrocardiographic signal detection device includes a small-sized housing capable of being lifted up by one hand. An IC chip, a memory, etc., which have the function of performing a simplified analysis of the electrocardiographic data, are contained in the housing. Several, e.g., two or three, electrodes, a small-sized liquid crystal display panel, an operating button, etc. are arranged on an outer surface of the housing. A user puts the fingers or the palms of the hands on the electrodes of the electrocardiographic signal detection device and then operates the operating button. Responsively, the electrocardiographic signal detection device detects an electrocardiographic signal of the user and generates electrocardiographic data, etc. Although the electrocardiographic data generated by the small-sized electrocardiographic signal detection device is simpler than that generated by the large-sized electrocardiographic signal detection device described above, the former data is also useful as, e.g., information for notifying a doctor of symptoms of heart diseases, such as palpitation (see Patent Documents 1 to 3).    Patent Document 1: Japanese Unexamined Patent Application Publication No. 11-299740    Patent Document 2: Japanese Unexamined Patent Application Publication No. 2003-144403    Patent Document 3: Japanese Unexamined Patent Application Publication No. 2005-46215
The electrodes employed in the above-described electrocardiographic signal detection device of the related art are each made of, e.g., metal including silver-silver chloride. When the electrocardiographic signal is detected, the electrodes are brought into direct contact with the human skin. After the detection of the electrocardiographic signal, the electrodes may be left to stand for a long time in some cases while the electrodes are exposed to open air in a state that moisture, etc. attributable to the contact with the human skin are kept adhering to the electrodes.
Therefore, if the electrocardiographic signal detection device is held in a poor management situation, there is a risk that durability may be reduced due to deterioration of the electrodes. Also, there is a risk that when an electrocardiogram is measured using the deteriorated electrodes, accuracy of the measurement may be degraded.
In the above-described portable electrocardiographic signal detection device of the related art, the plurality of electrodes need to be arranged on an outer surface of the housing such that the user can easily make contact, e.g., the fingers or the palms contact with the electrodes. Thus, a space sufficient to arrange the electrodes in a desired layout has to be secured on the outer surface of the housing. For that reason, it is difficult to realize a further reduction in size of the electrocardiographic signal detection device.